Why does my furnace blow cold air?

Homeowners may be concerned when they notice their furnace blows out cool air when it’s supposed to be producing heat.

One of the reasons your furnace is producing cold air is because it’s getting started. When a furnace first begins to work, it pushes stagnant air out of the ducts. Ducts are often located in the attic or basement, areas that aren’t typically heated so the air that fills the ducts becomes cool. Once the furnace has pushed this “sitting air” out of the way, then warm air follows.

If your furnace continues to blow cold air even after it has been running for a while, there may be a bigger issue that needs to be addressed. The issue can be minor with a simple fix, but it can also be more severe so don’t ignore your furnace if you feel consistently cold air or find yourself cranking up that thermostat.

First, check your thermostat. Make sure the mode is set to “heat” and the fan to “auto.” The “auto” setting will ensure that the fan only runs when the furnace is producing heat, thus eliminating drafts. Check to make sure your desired temperature is set higher than the room temperature. The thermostat will only activate heat when it detects the room temperature has dropped below your desired temperature.

The next step is to check your air filter by pulling it out and holding it up to a light to see if there’s an accumulation of dust or hair. If the filter is dirty you should replace it with a clean filter right away. If the filter has become so dirty that adequate air cannot pass through it, the furnace will overheat and turn itself off as a safety measure. You should call a professional at that time to reset the furnace and inspect it for damage from overheating.

The final step is to perform a visual and audible inspection for proper operation. Most furnaces have a top door that can be easily removed by hand. Opening the door will expose the heating components necessary for a visual inspection. Have someone turn the thermostat off, wait 5 minutes, and turn it back on to the heat mode. As the furnace warms up you should see and hear the following in this order:

1) A small fan begin to run near the top of the furnace – this is called an induce draft motor and pulls harmful gas like carbon monoxide from the furnace and out of the flue.

2) A bright glowing orange light towards the bottom of the furnace or the sound of rapid sparking – both of these items are forms of ignitors and enable the furnace to start the flame.

3) A click and then ignition of flames – the click you hear is the valve releasing the gas and the flames ignite once that gas comes in contact with the ignitor.

4) The main fan come on and warm air circulate through the house.

If any of these steps do not occur, then a safety feature will be enabled to stop the furnace. At this point it’s advised to call a professional to fully diagnose the system for problems.

If we were to think of your furnace as the heart of the heating system, then your ducts could be considered the arteries and veins. If these ducts come loose, become crushed, twisted, or are undersized, it could lead to higher than normal utility bills, hot and cold spots in the house, or even worse…a furnace heart attack! Bardi offers duct testing to identify issues and offer solutions on how to improve or correct areas of concerns. Duct testing services as well as a full furnace performance report are provided at no charge with the Friends of Bardi maintenance plan. Contact us to find out what other benefits Friends of Bardi members receive.